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Power

Since the mixer unit is a hybrid digital/analog device, several power supplies are necessary. It is desirable to keep digital and analog supplies separate, as digital circuits tend to inject a lot of noise on to their power supply rails. A $\pm$ 7V power supply is necessary, since the mixer chips chosen can not operate outside of the range of $\pm$ 7.5V. The specifications of the system dictate that large signals from external devices (up to +24dBu) may be used with the system. This dictates that a $\pm$ 14V power supply be used for the rails of the input and output boards. Adding a +5V power supply for the digital elements of the system rounds out the power requirements of the system. Each board receives its return grounds from the power connector, not from any of the other connectors present on the board. All ground signals are connected at the power supply. This star grounding technique shall be employed to eliminate ground loop problems. Figure 31 shows the pinouts of the power connector for boards in the mixer unit.

Figure 31: 8 circuit Molex Mini-Fit Jr. connector, used for power distribution in the mixer unit.
\begin{figure}
\psfig{file=fig/mfit-jr-8.eps}
\vspace{0.25in}
\begin{tabu...
... N.C. \\
\hline
8 & GND (analog) \\
\hline
\end{tabular}
\end{figure}


next up previous contents
Next: Audio Signal Distribution Up: Mixer Unit Previous: Gain Structure Diagram   Contents
Steve Richardson 2000-07-06
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